Method and systems for an energy recovery and energy converting unit for an engine

ABSTRACT

Various methods and systems are provided for generating exhaust energy and converting exhaust energy to electrical energy while an engine is not running. In one example, a system for an engine comprises: a first turbocharger including a first compressor driven by a first turbine, the first turbine disposed in an exhaust of the engine; a fuel burner fluidly coupled to the exhaust upstream of the first turbine; a generator coupled to one of the first turbine or an auxiliary, second turbine fluidly coupled to the exhaust downstream of the fuel burner; and one or more bypass valves configured to adjust a flow of air that bypasses the engine and is delivered to the fuel burner.

BACKGROUND

Technical Field

Embodiments of the subject matter disclosed herein relate to an engineand operation of electrical components of the engine when the engine isnot running.

Discussion of Art

An engine system including an engine may include one or moreturbochargers for increasing a pressure of intake air delivered to theengine. Each turbocharger may include a turbine disposed in an exhaustpassage and a compressor disposed in an intake passage, where exhaustgases flowing through the turbine cause the turbine to rotate andconsequently rotate the compressor coupled with the turbine via a shaft.In some examples, an electrical generator may be coupled with theturbocharger or an auxiliary turbine within the exhaust passage.However, energy may only be recovered via the system during engineoperation. As a result, when a vehicle in which the engine is installedstops, the engine may continue to operate in idle in order to power oneor more electrical loads of the engine. However, engines may havereduced fuel efficiency at idle conditions, thereby increasing fuelconsumption and wear on engine components.

BRIEF DESCRIPTION

In one embodiment, a system for an engine comprises: a firstturbocharger including a first compressor driven by a first turbine, thefirst turbine disposed in an exhaust of the engine; a fuel burnerfluidly coupled to the exhaust upstream of the first turbine; agenerator coupled to one of the first turbine or an auxiliary, secondturbine fluidly coupled to the exhaust downstream of the fuel burner;and one or more bypass valves configured to adjust a flow of air thatbypasses the engine and is delivered to the fuel burner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a vehicle, for example, alocomotive, according to an embodiment of the invention.

FIG. 2 is a schematic diagram of an engine with an exhaust gasrecirculation system and two-stage turbocharger system, according to anembodiment of the invention.

FIG. 3 is a schematic diagram of an engine with a single-stageturbocharger system and an engine bypass passage, according to anembodiment of the invention.

FIG. 4 is a flow chart showing a method for operating aturbine-generator during engine operation, according to an embodiment ofthe invention.

FIG. 5 is a flow chart showing a method for operating a fuel burner anda turbine-generator and powering one or more electrical components whenan engine is not operating, according to an embodiment of the invention.

DETAILED DESCRIPTION

The following description relates to embodiments of a system for anengine, comprising: a first turbocharger including a first compressordriven by a first turbine, the first turbine disposed in an exhaust ofthe engine; a fuel burner fluidly coupled to the exhaust upstream of thefirst turbine; a generator coupled to one of the first turbine or anauxiliary, second turbine fluidly coupled to the exhaust downstream ofthe fuel burner; and a first bypass valve configured to adjust a flow ofair that bypasses the engine and is delivered to the fuel burner. In oneexample, the generator is an electrical generator configured to convertrotational energy produced by rotation of a turbine via exhaust gasesfrom the engine into electrical energy. As one example, the generatormay be coupled to a shaft of the first turbocharger. As another example,the generator may be coupled to a shaft of an auxiliary turbine (e.g.,not coupled to a compressor and therefore not a turbocharger turbine)fluidly coupled to the exhaust of the engine. In one example, the fuelburner may be a device configured to combust fuel injected into the fuelburner, thereby producing exhaust gases. As such, fuel combustion may beequivalent to fuel burning. In another example, the fuel burner may bean energy converter configured to produce exhaust gas when the engine isnot operating (e.g., when the engine is off and not combusting fuelwithin the engine cylinders).

FIG. 1 shows an embodiment of a vehicle in which an engine system may beinstalled. Energy recovered via a generator may be used to power one ormore electrical loads (e.g., electrical components of the enginesystem), as shown in FIG. 1. In one embodiment, as shown in FIG. 2, theengine system may include a two-stage turbocharger system and an exhaustgas recirculation (EGR) system. In this embodiment, a fuel burner may befluidly coupled to the exhaust passage, downstream of where the EGRpassage connects to the exhaust passage. Further, the engine systemshown in FIG. 2 may include an engine bypass passage disposed betweenthe intake and exhaust passages for providing intake air to the fuelburner when the engine is off. The fuel burner may be located within theengine bypass passage or fluidly coupled to the exhaust passage,downstream of where the engine bypass passage connects to the exhaustpassage. Additionally, one of the turbochargers of the two-stageturbocharger system or an additional, auxiliary turbine may include agenerator coupled thereto (e.g., coupled to a shaft of the turbine). Thegenerator may be configured to recover exhaust energy from the turbineit is coupled to. During engine operation, the turbine-generator maygenerate energy via exhaust gas resulting from combustion at thecylinders of the engine, as shown in the method presented at FIG. 4. Asshown in the method presented at FIG. 4, the engine may be shut downunder certain conditions and then the burner may be operated to produceexhaust gas (instead of the engine cylinders). A method for operatingthe fuel burner to produce exhaust gas, recovering energy from theproduced exhaust gas, and powering one or more electrical components ofthe engine system with the recovered energy is presented at FIG. 5.Additionally, air needed for combustion at the burner to produce exhaustgas may be delivered via the EGR passage by flowing intake air inreverse from the intake passage, through the EGR passage, and to theexhaust passage. In another embodiment, as shown in FIG. 3, the enginesystem may include a single-stage turbocharger system and no EGR system.However, in alternate embodiments, the system of FIG. 3 may include twoturbochargers. The engine system of FIG. 3 also includes an enginebypass passage disposed between the intake and exhaust passages forproviding intake air to the fuel burner when the engine is off. In thisway, via a turbine-generator, excess exhaust energy from enginecombustion may be recovered during engine operation and used to powerthe engine, turbine, and/or additional electrical components.Additionally, during idle conditions when the engine is stationary, theengine may be shut down and electrical loads (e.g., components) of theengine may still be run via electrical energy from the sameturbine-generator (produced via exhaust gases from combustion at thefuel burner and not the engine). As a result, engine fuel consumptionmay be reduced while maintaining operation of desired electricalcomponents of the engine system.

The approach described herein may be employed in a variety of enginetypes, and a variety of engine-driven systems. Some of these systems maybe stationary, while others may be on semi-mobile or mobile platforms.Semi-mobile platforms may be relocated between operational periods, suchas mounted on flatbed trailers. Mobile platforms include self-propelledvehicles. Such vehicles can include on-road transportation vehicles, aswell as mining equipment, marine vessels, rail vehicles, and otheroff-highway vehicles (OHV). For clarity of illustration, a locomotive isprovided as an example of a mobile platform supporting a systemincorporating an embodiment of the invention.

Referring to FIG. 1, a schematic representation of a vehicle 10 movingfrom a first operating point to a second operating point along apredefined path is disclosed. In the illustrated embodiment, the vehicleis a rail vehicle, such as a locomotive. For example, as depicted inFIG. 1, the rail vehicle is configured to run on a rail 17 via aplurality of wheels 15. Suitable vehicles include passenger andnon-passenger vehicles, hybrid vehicles, off-highway vehicles, on-roadvehicles (such as tractor trailers), tracked vehicles, rail vehicles,and the like. The vehicle includes an engine 12 and an exemplary controlsystem 14 coupled to the engine. In one embodiment, the engine may be adual fuel engine.

In one embodiment, the vehicle is driven by the engine utilizing aplurality of fuels. In the exemplary engine, a reduction in nitrogenoxide (NOx) and particulate matter (PM) emissions is enabled bycombusting a relatively larger fraction of the premixed fuel. Forexample, in some embodiments, diesel and natural gas may be utilized todrive the engine. It should be noted herein that in certain embodiments,the vehicle may also utilize other fuels instead of diesel and naturalgas. A ratio of secondary fuel (e.g., natural gas) to total fuel(secondary fuel and primary fuel (e.g., diesel fuel)) delivered to theengine for combustion may be referred to herein as a substitution ratio.

In one embodiment, the rail vehicle is a diesel-electric vehicle. Asdepicted in FIG. 1, the engine is coupled to an electric powergeneration system, which includes an alternator/generator 11 andelectric traction motors 13. For example, the engine is a diesel and/ornatural gas engine that generates a torque output that is transmitted tothe alternator/generator which is mechanically coupled to the engine.

The alternator/generator produces electrical power that may be storedand applied for subsequent propagation to a variety of downstreamelectrical components. As an example, the alternator/generator may beelectrically coupled to a plurality of traction motors and thealternator/generator may provide electrical power to the plurality oftraction motors. As depicted, the plurality of traction motors are eachconnected to one of the plurality of wheels to provide tractive power topropel the rail vehicle. One example configuration includes one tractionmotor per wheel set. As depicted herein, six traction motors correspondto each of six pairs of motive wheels of the rail vehicle. In anotherexample, alternator/generator may be coupled to one or more resistivegrids 19. The resistive grids may be configured to dissipate excessengine torque via heat produced by the grids from electricity generatedby alternator/generator. In alternate embodiments, excess engine torquemay be dissipated to an alternate component, such as an energy storagedevice or additional electrical components 22, 23, and 24. As anexample, and as shown in FIG. 1, the additional electrical componentspowered by the alternator/generator may include one or more ofcompressors, blowers, batteries, and controllers (such as a controllerof the control system or additional vehicle controllers).

The vehicle additionally includes a turbine-generator 25. The turbinegenerator may include an electrical generator coupled to a shaft of aturbine adapted to rotate via exhaust passing through the turbine.Further details of the turbine-generator (also referred to herein as agenerator) are described below in reference to FIGS. 2-5. Examplepositioning of the turbine-generator in an engine system is shown inFIGS. 2 and 3. As shown in FIG. 1, the turbine-generator is electricallycoupled to the additional electrical components of the vehicle (whichmay include the engine control system). As described further below, whenthe engine is off (e.g., shut down and not combusting fuel to produceexhaust gas), the turbine-generator may still produce energy via exhaustenergy provided via a fuel burner (shown in FIGS. 2 and 3). Energy maythen be provided to the electrical components of the vehicle, while theengine is off, from the turbine-generator. The turbine-generator mayalso be coupled to the engine to provide power to the engine duringengine operation, as shown in FIG. 1.

The control system 14 is configured to adjust exhaust flow to theturbine-generator during engine operation (e.g., via one or more valves,as explained further below with reference to FIGS. 2-3). Additionally,the control system is configured to adjust one or more engine bypassvalves to flow intake air to a fuel burner disposed with an exhaust ofthe engine, operate the fuel burner to produce exhaust gas when theengine is off (e.g., via injecting fuel into the fuel burner), recoverenergy from the produced exhaust via the turbine-generator, and actuatethe turbine-generator to provide power to one or more electricalcomponents while the engine is off. The control system and methods forcontrolling the turbine-generator and fuel burner of the engine areexplained in greater detail below with reference to subsequent figures.

FIG. 2 presents a block diagram of an exemplary embodiment of an enginesystem 101 with an engine 104 (similar to engine 12 described above withreference to FIG. 1). The engine receives intake air for combustion froman intake, such as an intake manifold 115. The intake may be anysuitable conduit or conduits through which gases flow to enter theengine. For example, the intake may include the intake manifold, theintake passage 114, and the like. The intake passage may receive ambientair from an air filter (not shown) that filters air from outside of avehicle in which the engine may be positioned (such as vehicle 10 shownin FIG. 1). Exhaust gas resulting from combustion in the engine issupplied to an exhaust, such as the exhaust passage 116. The exhaust maybe any suitable conduit through which gases flow from the engine. Forexample, the exhaust may include an exhaust manifold, the exhaustpassage, and the like. Exhaust gas flows through the exhaust passage. Inone embodiment, the exhaust passage includes a NOx and/or oxygen sensorfor measuring a NOx and oxygen level of the exhaust gas.

In the example embodiment depicted in FIG. 2, the engine is a V-12engine having twelve cylinders. In other examples, the engine may be aV-6, V-8, V-10, V-16, I-4, I-6, I-8, opposed 4, or another engine type.As depicted, the engine includes a subset of non-donor cylinders 105,which includes six cylinders that supply exhaust gas exclusively to anon-donor cylinder exhaust manifold 117, and a subset of donor cylinders107, which includes six cylinders that supply exhaust gas exclusively toa donor cylinder exhaust manifold 119. In other embodiments, the enginemay include at least one donor cylinder and at least one non-donorcylinder. For example, the engine may have four donor cylinders andeight non-donor cylinders, or three donor cylinders and nine non-donorcylinders. It should be understood, the engine may have any desirednumbers of donor cylinders and non-donor cylinders, with the number ofdonor cylinders typically lower than the number of non-donor cylinders.In another example, the engine may not include any donor cylinders andinstead exhaust from all the engine cylinder may be routed to a commonexhaust passage (for example, an EGR system as described further belowmay be coupled to at least a portion of the common exhaust passage).

As depicted in FIG. 2, the non-donor cylinders are coupled to theexhaust passage to route exhaust gas from the engine to atmosphere(after it passes through first and second turbochargers 120 and 124).The donor cylinders, which provide engine exhaust gas recirculation(EGR), are coupled exclusively to an EGR passage 162 of an EGR system160 which routes exhaust gas from the donor cylinders to the intakepassage of the engine, and not to atmosphere. By introducing cooledexhaust gas to the engine, the amount of available oxygen for combustionis decreased, thereby reducing combustion flame temperatures andreducing the formation of nitrogen oxides (e.g., NOR).

In the example embodiment shown in FIG. 2, when a second valve 171 isopen, exhaust gas flowing from the donor cylinders to the intake passagepasses through a heat exchanger such as an EGR cooler 166 to reduce atemperature of (e.g., cool) the exhaust gas before the exhaust gasreturns to the intake passage. The EGR cooler may be an air-to-liquidheat exchanger, for example. In such an example, one or more charge aircoolers 132 and 134 disposed in the intake passage (e.g., upstream ofwhere the recirculated exhaust gas enters) may be adjusted to furtherincrease cooling of the charge air such that a mixture temperature ofcharge air and exhaust gas is maintained at a desired temperature. Inother examples, the EGR system may include an EGR cooler bypass.Alternatively, the EGR system may include an EGR cooler control element.The EGR cooler control element may be actuated such that the flow ofexhaust gas through the EGR cooler is reduced; however, in such aconfiguration, exhaust gas that does not flow through the EGR cooler isdirected to the exhaust passage rather than the intake passage.

Further, the EGR system includes a first valve (which may be referred toherein as a bypass valve) 164 disposed between the exhaust passage andthe EGR passage. The second valve may be an on/off valve controlled bythe controller 130 (for turning the flow of EGR on or off), or it maycontrol a variable amount of EGR, for example. In some examples, thefirst valve may be actuated such that an EGR amount is reduced (exhaustgas flows from the EGR passage to the exhaust passage). In otherexamples, the first valve may be actuated such that the EGR amount isincreased (e.g., exhaust gas flows from the exhaust passage to the EGRpassage). In some embodiments, the EGR system may include a plurality ofEGR valves or other flow control elements to control the amount of EGR.

In such a configuration, during engine operation (e.g., when the enginecylinders are combusting), the first valve is operable to route exhaustfrom the donor cylinders to the exhaust passage of the engine and thesecond valve is operable to route exhaust from the donor cylinders tothe intake passage of the engine. Additionally, when the engine is offand not combusting fuel, the first valve and second valve may beoperable to route intake air from the intake passage to the exhaustpassage (e.g., in a reverse direction through the EGR passage). Thisoperation of the first and second valves of the EGR system during engineoff periods is discussed further below.

In the example embodiment shown in FIG. 2, the first valve and thesecond valve may be engine oil, or hydraulically, actuated valves, forexample, with a shuttle valve (not shown) to modulate the engine oil. Insome examples, the valves may be actuated such that one of the first andsecond valves and is normally open and the other is normally closed. Inother examples, the first and second valves and may be pneumatic valves,electric valves, or another suitable valve.

As shown in FIG. 2, the engine system further includes an EGR mixer 172which mixes the recirculated exhaust gas with charge air such that theexhaust gas may be evenly distributed within the charge air and exhaustgas mixture. In the example embodiment depicted in FIG. 2, the EGRsystem is a high-pressure EGR system which routes exhaust gas from alocation upstream of the turbochargers in the exhaust passage to alocation downstream of the turbochargers in the intake passage. In otherembodiments, the engine system may additionally or alternatively includea low-pressure EGR system which routes exhaust gas from downstream ofthe turbochargers in the exhaust passage to a location upstream of theturbochargers in the intake passage. Additionally, in some embodiments,the engine system may not include the EGR mixer.

As depicted in FIG. 2, the engine system further includes a two-stageturbocharger with the first turbocharger 120 and the second turbocharger124 arranged in series, each of the turbochargers arranged between theintake passage and the exhaust passage. The two-stage turbochargerincreases air charge of ambient air drawn into the intake passage inorder to provide greater charge density during combustion to increasepower output and/or engine-operating efficiency. The first turbochargeroperates at a relatively lower pressure, and includes a first turbine121 which drives a first compressor 122. The first turbine and the firstcompressor are mechanically coupled via a first shaft 123. The secondturbocharger operates at a relatively higher pressure, and includes asecond turbine 125 which drives a second compressor 126. The secondturbine and the second compressor are mechanically coupled via a secondshaft 127. In the example embodiment shown in FIG. 2, the secondturbocharger is provided with a wastegate 128 disposed in a secondbypass passage 129 which allows exhaust gas to bypass the secondturbocharger. The wastegate may be opened, for example, to divert theexhaust gas flow away from the second turbine. In this manner, therotating speed of the compressors, and thus the boost provided by theturbochargers to the engine may be regulated during steady stateconditions. In another embodiment, the wastegate may be a three-wayvalve disposed at the junction between the exhaust passage and thesecond bypass passage. As such, the wastegate may be adjusted toincrease flow through the second bypass passage and reduce flow to thesecond turbocharger. In other embodiments, each of the turbochargers maybe provided with a wastegate, or only the second turbocharger may beprovided with a wastegate.

As explained above, the terms “high pressure” and “low pressure” arerelative, meaning that “high” pressure is a pressure higher than a “low”pressure. Conversely, a “low” pressure is a pressure lower than a “high”pressure.

The engine system further includes a turbine-generator (such as theturbine-generator 25 shown in FIG. 1). The turbine-generator includes anelectrical generator 145 coupled to a shaft of a turbine. Exhaustpassing through the turbine rotates the turbine and, in turn, rotatesthe shaft. The generator coupled to the shaft then converts therotational energy to electrical energy. The generator is electricallycoupled to one or more electrical components 131 of the engine system orvehicle. As described above, the one or more electrical components mayinclude one or more heaters, compressors, blowers, batteries,controllers (which may include controller 130). The generator may alsoprovide electrical power to the engine to assist in cranking the engine.

FIG. 2 shows a plurality of alternate locations that the generator 145may be positioned. In one embodiment, the engine system may only includeone generator coupled to any one of the locations shown in FIG. 2. Inalternate embodiments, the engine system may include two or moregenerators coupled to two or more of the locations shown in FIG. 2. Asshown in FIG. 2, the generator may be coupled to the first shaft of thefirst turbocharger or the second shaft of the second turbocharger. Theengine system may include an additional, auxiliary turbine that is notcoupled with a compressor (and thus not a turbocharger turbine). Forexample, as shown in FIG. 2, a first auxiliary turbine 142 may bepositioned in the second bypass passage around the second turbine. Assuch, the first auxiliary turbine is positioned in parallel with thesecond turbine. The wastegate in the second bypass passage may controlan amount of exhaust gas flowing through the first auxiliary turbine.Further, as shown in FIG. 2, the exhaust passage may include a firstauxiliary valve 197 to control the amount of exhaust gas flowing throughthe first auxiliary turbine (for example, the first auxiliary valve maybe closed to divert all exhaust through the first auxiliary turbine whenthe engine is off, as described further below). In another example, asshown in FIG. 2, a second auxiliary turbine 143 may be positioned in afirst bypass passage 146 around the first turbine. As such, the secondauxiliary turbine is positioned in parallel with the first turbine. Thefirst bypass passage includes a first bypass valve 147 configured tocontrol an amount of exhaust gas flowing through the second auxiliaryturbine. In some examples, the engine may include an additional valvedisposed in the exhaust passage, such as second auxiliary valve 198, orthe first bypass valve may be a three-way valve disposed at the junctionbetween the exhaust passage and the first bypass passage, to control theamount of exhaust gas flowing to first turbine arranged in parallel withthe second auxiliary turbine. In yet another example, as shown in FIG.2, a third auxiliary turbine 144 is disposed in the exhaust passage,downstream of the first turbine and second turbine. Thus, the thirdauxiliary turbine is positioned in series with the first turbine andsecond turbine. The engine system may include none or one or more of thefirst, second, and third auxiliary turbines. The generator may becoupled to the first, second, or third auxiliary turbines via a shaft ofthe corresponding turbine. As such, the engine system may include aturbine-generator including any one of or one or more of: the firstturbine 121 and generator; the second turbine 125 and generator; thefirst auxiliary turbine 142 and generator; the second auxiliary turbine143 and generator; and the third auxiliary turbine 144 and generator.

The engine system further includes a fuel burner 140 fluidly coupled tothe exhaust passage. As shown in FIG. 2, the fuel burner 140 may becoupled directly in the exhaust passage such that all exhaust gasesflowing through the exhaust passage pass through the fuel burner.Alternatively, the fuel burner may be disposed in a bypass passage 148,the bypass passage directly coupled to the exhaust passage. In thisembodiment, the bypass passage may include a bypass valve 141 configuredto adjust an amount of exhaust flowing from the exhaust passage andthrough the fuel burner. In yet another embodiment, the fuel burner maybe disposed within a second engine bypass passage 191, as describedfurther below. The fuel burner may include a fuel injector for injectingfuel into a combustion chamber of the fuel burner. The fuel burner mayadditionally include a spark plug or alternate means of burning theinjected fuel and air within the fuel burner. In this way, the fuelburner is adapted to burn (e.g., combust) air and fuel within the fuelburner to produce exhaust gas.

The engine system further includes an engine bypass passage coupledbetween the intake passage and exhaust passage of the engine. FIG. 2shows two alternate locations for the engine bypass passage. As oneexample, the engine bypass passage may be first engine bypass passage195 with a first end of the first engine bypass passage coupled to theintake passage, downstream of the second compressor and a second end ofthe first engine bypass passage coupled to the exhaust passage, upstreamof the fuel burner, second turbine, and one or more auxiliary turbines.A first engine bypass valve 194 is positioned within the engine bypasspassage and operable to control a flow of intake air from the intakepassage to the exhaust passage when the engine is off and not combustingfuel (e.g., the controller may actuate the engine bypass valve to adjustan amount of air flowing to the fuel burner for combustion when theengine is not operating). Additionally, the intake passage may include asecond engine bypass valve 193 disposed in the intake passage,downstream of the first end of the first engine bypass passage andupstream of the charge air cooler 134. The exhaust passage may alsoinclude a third engine bypass valve 196 disposed in the exhaust passage,upstream of the second end of the first engine bypass passage. Duringengine operation, the controller may maintain the first engine bypassvalve in a closed position and the second and third engine bypass valvesin an open position to reduce the flow of air between the exhaustpassage and intake passage via the first engine bypass passage whileallowing intake airflow to the engine for combustion. When the engine isoff, the controller may open the first engine bypass valve while closingthe second and third engine bypass valves in order to flow intake air tothe fuel burner and not flow intake air to the engine. A method fordirecting intake air to the fuel burner when the engine is shut down isdescribed further below with reference to FIG. 5.

As another example, the engine bypass passage may be second enginebypass passage 191 with a first end of the second engine bypass passagecoupled to the intake passage, downstream of the first compressor and asecond end of the second engine bypass passage coupled to the exhaustpassage, upstream of the first turbine and one or more auxiliaryturbines. In this embodiment, the fuel burner 140 is disposed within thesecond engine bypass passage. Additionally, in this embodiment, theintake passage may include a fourth engine bypass valve 190 disposed inthe intake passage, downstream of the first end of the second enginebypass passage and upstream of both charge air coolers (if there aretwo). The exhaust passage may also include a fifth engine bypass valve192 disposed in the exhaust passage, upstream of the second end of thefirst engine bypass passage. During engine operation, the controller maymaintain the fuel burner off (and closed to airflow) and the fourth andfifth engine bypass valves in an open position to reduce the flow of airbetween the exhaust passage and intake passage via the second enginebypass passage while allowing intake airflow to the engine forcombustion. For example, the second engine bypass passage may include abypass passage valve 199 for adjusting air flow through the secondengine bypass passage (e.g., such as closing the bypass passage valve inthe second engine bypass passage during engine operation to block flowthrough the second engine bypass passage). When the engine is off, thecontroller may operate the fuel burner while opening the bypass passagevalve and closing the fourth and fifth engine bypass valves in order toflow intake air through the fuel burner (and exhaust gas from the fuelburner to the turbine-generator) and not flow intake air or producedexhaust gas to the engine. In both embodiments of the engine bypasspassage shown in FIG. 2, the intake air is routed directly from anoutlet of one of the compressors and to an inlet of the fuel burner.This routing may increase the thermodynamic performance of the fuelburner.

The engine system further includes a controller 130 (e.g., may also bereferred to as a control system, such as control system 14 of FIG. 1) tocontrol various components related to the vehicle system. In oneexample, the controller includes a computer control system. In oneembodiment, the computer control system includes a processor, such asprocessor 136. The controller may include multiple engine control units(ECU) and the control system may be distributed among each of the ECUs.The controller further includes computer readable storage media, such asmemory 138, including instructions for enabling on-board monitoring andcontrol of rail vehicle operation. The memory may include volatile andnon-volatile memory storage.

The controller may oversee control and management of the vehicle system.The controller may receive signals from a variety of engine sensors 139to determine operating parameters and operating conditions, andcorrespondingly adjust various engine actuators 137 to control operationof the vehicle. For example, the controller may receive signals fromvarious engine sensors including engine speed, engine load, boostpressure, exhaust pressure, ambient pressure, exhaust temperature, etc.Correspondingly, the controller may control the vehicle system bysending commands to various components such as traction motors,alternator, cylinder valves, throttle, etc.

As one example, during engine operation (e.g., when the engine is on andcombusting fuel at the engine cylinders) the controller may receivesignals from one or more engine sensors (e.g., such as an engine speedsensor, engine load sensor, or turbocharger speed sensor) and determinethat engine assist is desired. As such, the controller may operate theturbine-generator to produce energy and provide the produced energy tothe engine via actuating one or more valves (such as wastegate 128,first bypass valve 147, first valve 164, first auxiliary valve 197,second auxiliary valve 198, and/or second valve 171) to direct exhaustgas to the turbine of the turbine-generator. During engine operation, ifthe fuel burner is positioned in the bypass passage, the controller mayadditionally close the bypass valve of the bypass passage to reduceexhaust gas flowing through the fuel burner.

The controller may additionally stop operating the engine (via stoppinginjecting and combusting fuel at the engine cylinders) in response tothe engine being stationary (e.g., the vehicle in which the enginesystem is installed being stationary). Alternatively, if the engine is astationary engine, the controller may stop operating the engine inresponse to only needing to supply auxiliary electrical power and notcombustive power. As introduced above, when the engine is off and notcombusting fuel, the controller may actuate one or more engine bypassvalves to route intake air from the intake passage to the exhaustpassage. In an alternate embodiment, during this condition, thecontroller may actuator the first valve 164 and second valve 171 toroute intake air from the intake passage to the exhaust passage.Additionally, while the engine is off, the controller may direct theintake air to the fuel burner and operate the fuel burner to produceexhaust gas (e.g., via turning on the fuel burner and/or actuating oneor more actuators of the fuel burner to inject fuel and combust fuel andair within the fuel burner). Further still, while the engine is off, thecontroller may direct exhaust gas from the fuel burner to theturbine-generator (e.g., via actuating one or more valves controllingexhaust flow to the turbine of the turbine-generator as explainedabove). The controller may also send signals to the generator of theturbine-generator to provide electrical energy to one or more electricalcomponents based on electrical loads of the one or more electricalcomponents.

FIG. 3 shows an alternate configuration of an engine system 301 that maybe used in a vehicle, such as vehicle 10 shown in FIG. 1. The enginesystem shown in FIG. 3 only includes a single turbocharger and does notinclude an EGR system. However, in alternate embodiments, the enginesystem may include an EGR system or additional turbochargers. The enginesystem shown in FIG. 3 includes similar components to that of enginesystem 101 shown in FIG. 2. As such, similar components have beennumbered similarly in FIG. 3 and will not be re-described below ifalready introduced above with reference to FIG. 2.

In the example embodiment depicted in FIG. 3, the engine is a V-12engine having twelve cylinders. In other examples, the engine may be aV-6, V-8, V-10, V-16, I-4, I-6, I-8, opposed 4, or another engine type.As depicted, the engine includes a first set of cylinders 105, whichincludes six cylinders that supply exhaust gas exclusively to a firstcylinder exhaust manifold 117, and another subset of cylinders 207,which includes six cylinders that supply exhaust gas exclusively to asecond cylinder exhaust manifold 119. All the engine cylinders arecoupled to the exhaust passage 116 and thus route exhaust gas from theengine to atmosphere (after it passes through turbocharger 124).

As depicted in FIG. 3, the engine system further includes a single-stageturbocharger with the turbocharger 124 arranged between the intakepassage and the exhaust passage. The turbocharger includes a turbine 125which drives a compressor 126. The turbine and the compressor aremechanically coupled via a shaft 127.

The engine system further includes a turbine-generator (such as theturbine-generator 25 shown in FIG. 1 and the turbine-generator describedabove with reference to FIG. 2). The turbine-generator includes anelectrical generator 145 coupled to a shaft of a turbine. Theturbine-generator of FIG. 3 may operate similarly to theturbine-generator of FIG. 2, as described above.

FIG. 3 shows a plurality of alternate locations that the generator 145may be positioned. In one embodiment, the engine system may only includeone generator coupled to any one of the locations shown in FIG. 3. Inalternate embodiments, the engine system may include two or moregenerators coupled to two or more of the locations shown in FIG. 3. Asshown in FIG. 3, the generator may be coupled to the shaft of theturbocharger. The engine system may include an additional, auxiliaryturbine that is not coupled with a compressor (and thus not aturbocharger turbine). For example, as shown in FIG. 3, a firstauxiliary turbine 142 may be positioned in a first bypass passage 146around the turbine of the turbocharger. As such, the first auxiliaryturbine is positioned in parallel with the turbocharger turbine. Thefirst bypass passage includes a first bypass valve 147 configured tocontrol an amount of exhaust gas flowing through the first auxiliaryturbine. In another example, as shown in FIG. 3, a second auxiliaryturbine 144 is disposed in the exhaust passage, downstream of theturbocharger turbine. Thus, the second auxiliary turbine is positionedin series with the turbocharger turbine. The engine system may includenone or one or more of the first and second auxiliary turbines. Thegenerator may be coupled to the first or second auxiliary turbines via ashaft of the corresponding turbine. As such, the engine system mayinclude a turbine-generator including any one of or one or more of: theturbocharger turbine 125 and generator; the first auxiliary turbine 142and generator; and the second auxiliary turbine 144 and generator.

The engine system further includes a fuel burner 140 and controller 130,as described above with reference to FIG. 3. Additionally, the enginesystem of FIG. 3 includes an engine bypass passage 195 disposed betweenthe intake passage and exhaust passage. Specifically, a first end of theengine bypass passage is coupled to the intake passage, downstream ofthe turbocharger compressor and a second end of the engine bypasspassage is coupled to the exhaust passage, upstream of the fuel burner,turbocharger turbine, and one or more auxiliary turbines. A first enginebypass valve 194 is positioned within the engine bypass passage andoperable to control a flow of intake air from the intake passage to theexhaust passage when the engine is off and not combusting fuel (e.g.,the controller may actuate the first engine bypass valve to adjust anamount of air flowing to the fuel burner for combustion when the engineis not operating). Additionally, the intake passage may include a secondengine bypass valve 193 disposed in the intake passage, downstream ofthe first end of the first engine bypass passage and upstream of thecharge air cooler 134. The exhaust passage may also include a thirdengine bypass valve 196 disposed in the exhaust passage, upstream of thesecond end of the first engine bypass passage. During engine operation,the controller may maintain the first engine bypass valve in a closedposition and the second and third engine bypass valves in an openposition to reduce the flow of air between the exhaust passage andintake passage via the first engine bypass passage while allowing intakeairflow to the engine for combustion. When the engine is off, thecontroller may open the first engine bypass valve while closing thesecond and third engine bypass valves in order to flow intake air to thefuel burner and not flow intake air to the engine. A method fordirecting intake air to the fuel burner when the engine is shut down isdescribed further below with reference to FIG. 5. In an alternateembodiment, the first engine bypass valve may be a three-way valvepositioned at the junction between the engine bypass passage and theintake passage and the intake passage may then not include the secondengine bypass valve.

Turning to FIG. 4, a flow chart of a method 400 for operating aturbine-generator during engine operation is shown. As one example, theturbine-generator is one of the turbine-generators described above withreference to FIG. 2 and FIG. 3. Method 400 also presents a method forshutting down the engine under certain conditions. Method 400 and therest of the methods described herein may be executed by an enginecontroller (such as controller 130 shown in FIGS. 2-3) according toinstructions stored on a memory of the controller, in combination withvarious sensors and actuators of the engine system (such as enginesystem 101 shown in FIG. 2 or engine system 301 shown in FIG. 3).

At 402, the method includes estimating and/or measuring engine operatingconditions. Engine operating conditions may include engine speed and/orload, engine temperature, an electrical load of one or more engine orvehicle electrical components, a speed of a vehicle in which the enginesystem is installed, turbocharger speed, a rotational speed of aturbine-generator, or the like. At 404, the method includes determiningif engine assistance is needed. In one example, the controller maydetermine that engine assistance is needed in response to engine loadand an amount of energy stored at the generator. For example, thecontroller may determine that engine assistance is needed when engineload is over a threshold load and there is a threshold amount of energystored at the generator.

If energy assistance at the engine is not requested, the methodcontinues to 406 to determine whether there is an opportunity togenerate energy with the turbine-generator. In one example, thecontroller may determine that there is an opportunity to generate energywith the turbine-generator when the turbine-generator includes a turbinedisposed directly in the exhaust passage (e.g., not in a bypass passagearranged in parallel with the exhaust passage) and exhaust is flowingthrough the turbine. In another example, the controller may determinethat there is an opportunity to generate energy with theturbine-generator when the turbine-generator includes a turbine disposedin a bypass passage around the turbocharger turbine and a speed of theturbocharger turbine is greater than desired for torque demand. If thereis not an opportunity to generate energy via the turbine-generator, themethod continues to 407 to maintain current engine operation.Alternatively at 406, if there is an opportunity to generate energy viathe turbine-generator, the method continues to 408 to generate energyvia the turbine-generator and store energy at the generator. The methodat 408 may include directing exhaust gas flow to the turbine of theturbine-generator via adjusting one or more valves disposed upstream ofthe turbine (e.g., such as adjusting bypass valve 128 if theturbine-generator includes turbine 142, as shown in FIG. 2). Therotational energy of the turbine and turbine shaft may then be convertedto electrical energy by the generator. From 408 and 407, the methodcontinues to 412, as described further below. In some examples, method400 may further include, in response to the speed of the turbochargerturbine being less than desired for torque demand, supplying energy fromthe generator to the turbocharger turbine to increase the speed of theturbocharger turbine.

Returning to 404, if engine assist is requested, the method continues to410 to operate the turbine-generator to produce energy and provide theproduced energy to the engine to assist the engine (e.g., via providingcranking assistance) and/or supply stored energy from the generator tothe engine. The method at 410 may include directing exhaust gas to theturbine of the turbine-generator in order to increase rotation of theturbine and recover the rotational energy at the generator. At 412, themethod includes determining if the engine is stationary. In one example,the controller may determine that the engine is stationary if vehiclespeed of a vehicle in which the engine is installed is less than athreshold speed. In one example, the threshold speed may beapproximately zero. In another example, the threshold speed may begreater than zero. If the engine is stationary, engine combustion maynot be required for propelling the vehicle. The method at 412 mayadditionally or alternatively include determining whether a demandedpower level (e.g., operator demanded power level) of the engine is lessthan a threshold. For example, the threshold power level may be a levelat which combustion of fuel at the engine is not required to support oneor more power demands of the engine.

If the engine is not stationary and/or the demanded power level isgreater than the threshold, the method continues to 414 to continuecurrent engine operation and then the method ends. Alternatively, if theengine is stationary and/or the demanded power level is at or less thanthe threshold, the method continues to 416 to determine the electricaldemand of one or more electrical components of the engine and/or vehicleand an amount of energy stored at the generator of the turbine-generator(e.g., a storage level of a battery of the generator).

At 418, the method includes determining if it is advantageous to shutdown the engine. For example, when the engine is stationary, the enginemay operate in idle and continue to consume fuel. However, operating theengine in idle may result in reduced fuel economy and increased stresson engine components, as well as increased emissions. Alternatively, theengine may be shut down and therefore stop injecting fuel and combustingthe injected fuel. This may reduce fuel consumption and emissions of theengine. In one example, it may be advantageous to shut down the engineif the electrical loads of the one or more electrical components aregreater than a threshold level. In another example, it may beadvantageous to shut down the engine if the fuel savings from notcombusting fuel at the engine cylinders outweighs the fuel usage inrunning the fuel burner to power the electrical loads. In yet anotherexample, it may not be advantageous to shut down the engine if the onlyelectrical load to be powered while the engine is stationary is anelectrical load of a heater (e.g., to heat the vehicle cabin). If thecontroller determines that it is not advantageous to shut down theengine, the method continues to 420 to continue to operate the engine inidle. Alternatively, if the controller determines that it isadvantageous to shut down the engine, the method continues to 422 toshut down the engine and operate the fuel burner and turbine-generatorto produce and supply electrical energy to the one or more electricalcomponents and/or supply power to additional components using theproduced exhaust energy. The method at 422 is expanded upon in method500 of FIG. 5, as discussed further below.

FIG. 5 shows a flow chart of a method 500 for operating the fuel burnerto produce exhaust gas, recovering energy from the produced exhaust gasvia the turbine-generator, and powering one or more electricalcomponents of the engine system with the recovered energy. Method 500may continue from method 400 presented at FIG. 4. As explained above,the turbine-generator may be one of the turbine-generators shown in FIG.2 or 3. Additionally, the fuel burner may be a fuel burner disposed inan engine bypass passage or an exhaust passage, upstream of theturbine-generator, such as one of the fuel burners 140 shown in FIG. 2or 3. The engine bypass passage (such as the EGR passage 162 shown inFIG. 2 or engine bypass passages 195 or 191 shown in FIGS. 2 and 3) fordirecting intake air from the intake passage to the exhaust passage,upstream of the fuel burner, in order to provide air to the burner forcombusting fuel and producing exhaust gas.

Method 500 starts at 502 where the method includes determining if thereis a request to shut down the engine and operate the fuel burner andturbine-generator to produce electrical energy (similar to as explainedabove at 418, 420, and 422 of method 400). If there is not a request toshut down the engine, the method continues to 504 to continue thecurrent engine operation and not shut down the engine. Alternatively, ifthere is a request to shut down the engine, the method continues to 506.At 506, the method includes starting (e.g., starting rotation of) theturbine coupled to the generator (e.g., starting the turbine of theturbine-generator). In one example, as shown at 508, starting theturbine coupled to the generator may include routing exhaust gas fromthe engine cylinders (before shutting down the engine) to the turbine ofthe turbine-generator in order to increase the speed of the turbine.Routing exhaust gas from the engine cylinders to the turbine of theturbine-generator may include actuating one or more valves disposed inthe exhaust passage or bypass passages in which the turbine-generator isinstalled to increase exhaust flow to the turbine-generator. In anotherexample, as shown at 508, starting the turbine coupled to the generatormay include using energy stored at the generator to rotate the shaft ofthe turbine and thus increase the speed of the turbine. The method thencontinues to 512 to shut down the engine. Shutting down the engine mayinclude stopping injecting fuel in the engine cylinders and stoppingcombustion at the engine cylinders. As a result, no more exhaust gas maybe produced by the engine cylinders.

At 514, the method includes routing intake air to the fuel burner. Inone example, routing intake air to the fuel burner may include actuatinga valve disposed in an engine bypass passage disposed between the intakepassage and exhaust passage (and one or more valves disposed in theintake passage and/or exhaust passage proximate to the engine bypasspassage) to increase a flow of intake air through the engine bypasspassage and to the fuel burner. As one example, actuating the valvedisposed in the engine bypass passage may include actuating the valve toincrease an opening of the valve (e.g., moving the valve from a closedto open position) and actuating the valve(s) disposed in the intakepassage and/or exhaust passage proximate to the engine bypass passagemay include actuating the valve(s) to decrease the opening of the valve(s) (e.g., moving the valves from an open to a closed position). In oneexample, the valve(s) disposed in the intake passage and/or exhaustpassage proximate to the engine bypass passage may include valves 193and 196 shown in FIGS. 2 and 3 or valves 190 and 192 shown in FIG. 2. Inone example, the engine bypass passage may be an EGR passage includingone or more EGR valves and/or an EGR cooler, such as the EGR passage 162shown in FIG. 2. In another example, the engine bypass passage may beone of engine bypass passages 191 or 195 shown in FIG. 2 or 3. Further,a first end of the engine bypass passage may be coupled to the intakepassage and a second end of the engine bypass passage may be coupled tothe exhaust passage upstream of the fuel burner. As a result, intake airflowing through the engine bypass passage is directed to the fuelburner. In one example, when the fuel burner is disposed in a bypasspassage arranged in parallel with the main exhaust passage, the methodat 514 further includes adjusting a valve disposed in the exhaustpassage and/or bypass passage to direct intake air to the fuel burner.

At 516, the method includes operating the fuel burner to produce exhaustgas. In one example, the method at 516 includes injecting fuel into acombustion chamber of the fuel burner and combusting (e.g., burning) theinjected fuel and intake air within the fuel burner to produce exhaustgas. As one example, the method at 518 includes operating the fuelburner while the engine and engine coolant are still hot. For example,the engine may be above a threshold temperature. Further, operating thefuel burner may be independent of coolant temperature and/or cabintemperature of the vehicle. At 518, the method includes routing theproduced exhaust gas from the fuel burner outlet to the turbine coupledto the generator (e.g., directing exhaust gas to the turbine-generator).In one example, when the turbine-generator is included on one of theturbocharger turbines, or an auxiliary turbine arranged in the mainexhaust passage, the method includes directing the produced exhaust gasthrough the exhaust passage to the turbine-generator. In anotherexample, when the turbine-generator is an auxiliary turbine located in abypass passage arranged in parallel with the main exhaust passage andone of the turbocharger turbines, the method at 518 includes adjustingone or more valves disposed in the bypass passage (and/or the exhaustpassage) to direct the exhaust gas through the bypass passage and to theturbine-generator and not through the turbocharger turbine arranged inparallel with the turbine-generator.

At 520, the method includes recovering exhaust energy via theturbine-generator and powering one or more electrical components withthe recovered energy. As one example, the method at 520 includesconverting rotational energy from the turbine shaft into electricalenergy at the generator and then supplying the energy to one or moreelectrical components based on an electrical demand of the one or moreelectrical components. As such, a larger amount of power may be suppliedto electrical components having larger electrical demands. At 522, themethod includes continuing to operate the fuel burner based onelectrical demands of the one or more electrical components. Forexample, an amount of fuel injected at the fuel burner and the amount ofintake air directed to the fuel burner may increase as the electricaldemand of the electrical components increases. Further, in one example,as shown at 524, the method may include continuously operating the fuelburner and adjusting the fuel and air directed to the fuel burner basedon the electrical demand of the electrical components. In anotherexample, as shown at 526, the method include cycling the fuel burner onand off based on the electrical demand of the electrical components (andthus not operating the burner continuously during a duration of theengine shut down). At 528, the method includes determining whether anengine start (e.g., restart) has been requested. For example, an enginestart may be requested if there is a request to provide power to thevehicle. If there is not a request to start the engine, the methodreturns to 522 to continue operating the fuel burner based on electricaldemands of the engine system. Alternatively, if there is a request tostart the engine, the method continues to 530 to stop operating the fuelburner, stop routing intake air to the burner, and restart the engine.

In this way, a turbine-generator may be used during engine operation torecover exhaust energy produced by cylinders of the engine and providethe recovered energy to one or more of the engine, electricalcomponents, or the turbine of the turbine-generator. Theturbine-generator may also be used when the engine is not operating, inconjunction with a fuel burner, to recover exhaust energy produced bythe fuel burner and provide the recovered exhaust energy to one or moreelectrical components of the engine. In one example, theturbine-generator may be included on one of the turbocharger turbines ofthe engine. In another example, the turbine-generator may be included asan additional, auxiliary turbine either in series or in parallel withthe one or more turbocharger turbines. In this way, the technical effectof shutting down the engine and providing power to one or moreelectrical components via the fuel burner and turbine-generator systemis to continue operating electrical components of the engine whilereducing fuel consumption of the engine. Engine wear may also be reducedby reducing engine idle periods. Further, a same turbine-generator maybe used during both engine operation and when the engine is off to powerelectrical components of the engine. This may reduce a number ofcomponents of the engine.

As one embodiment, a system for an engine comprises a first turbochargerincluding a first compressor driven by a first turbine, the firstturbine disposed in an exhaust of the engine; a fuel burner fluidlycoupled to the exhaust upstream of the first turbine; a generatorcoupled to one of the first turbine or an auxiliary, second turbinefluidly coupled to the exhaust downstream of the fuel burner; and one ormore bypass valves configured to adjust a flow of air that bypasses theengine and is delivered to the fuel burner. In one example, the systemmay further comprise an engine bypass passage coupled between an intakeof the engine and the exhaust, where the one or more bypass valvesinclude a first bypass valve disposed in an intake of the engine,downstream in the intake from where the engine bypass passage couples tothe intake, and a second bypass valve disposed in the exhaust, upstreamin the exhaust from where the bypass passage couples to the exhaust, andwhere the fuel burner is disposed within the bypass passage. In anotherexample, the exhaust is fluidly coupled to a plurality of non-donorcylinders of the engine and the one or more bypass valves is an exhaustgas recirculation (EGR) valve disposed in an EGR passage, where a firstend of the EGR passage is fluidly coupled to the exhaust and a secondend of the EGR passage is fluidly coupled to an intake of the engine,and where the EGR passage is configured to receive exhaust gas from adonor exhaust manifold coupled to a plurality of donor cylinders of theengine during engine operation. In yet another example, the exhaustincludes an exhaust passage directly coupled to the plurality ofnon-donor cylinders, the first end of the EGR passage is directlycoupled to the exhaust passage, and the fuel burner and first turbineare fluidly coupled to the exhaust passage. In one example, thegenerator is coupled to the second turbine and the second turbine ispositioned in series with the first turbine. In another example, thegenerator is coupled to the second turbine and the second turbine ispositioned in parallel with the first turbine. The system may furthercomprise a second turbocharger including a second compressor driven by athird turbine, the third turbine fluidly coupled to the exhaust andpositioned in series with the first turbine. Further, the fuel burnermay be fluidly coupled to the exhaust, upstream of both the secondturbocharger and the first turbocharger, the system may further comprisean engine bypass passage coupled between an intake of the engine,downstream in the intake from the first compressor and second compressorand upstream in the intake from a charge air cooler, and the exhaust,upstream in the exhaust from the fuel burner, the first turbine, and thesecond turbine, and the one or more bypass valves may include a firstbypass valve disposed in the engine bypass passage, a second bypassvalve disposed in the intake downstream from where the engine bypasspassage couples to the intake, and a third bypass valve disposed in theexhaust upstream from where the engine bypass passage couples to theexhaust. In an example, the generator is coupled to the second turbine,the second turbine is positioned in parallel with the first turbinewithin a bypass passage around the first turbine, and the system furthercomprises a second bypass valve disposed in the bypass passage aroundthe first turbine. The system may further comprise a controllerincluding non-transitory memory with computer-readable instructions foroperating the fuel burner to produce exhaust gas, adjusting the firstbypass valve to flow air from an intake of the engine to the fuelburner, and recovering exhaust energy from the produced exhaust gas viathe generator in response to the engine being shut down. The may alsofurther comprise an electrical component electrically coupled with thegenerator and the instructions may further include instructions foroperating the electrical component via energy stored at the generatorwhile the engine is shut down.

As another embodiment a method comprises, after shutting down an engineand while the engine is shut down: adjusting one or more valvesconfigured to adjust a flow of air through an engine bypass passage, theengine bypass passage fluidly coupled between an intake passage andexhaust passage of the engine, to flow air to a fuel burner fluidlycoupled to the exhaust passage upstream of a first turbocharger turbine;operating the fuel burner to produce exhaust gas; recovering exhaustenergy downstream of the fuel burner via a generator directly coupled toone of a shaft of the first turbocharger turbine, an auxiliary turbinecoupled in series with the first turbocharger turbine, or an auxiliaryturbine coupled in parallel with the first turbocharger turbine; andpowering one or more electrical components of the engine while theengine is shut down using the recovered exhaust energy. The method mayfurther comprise determining to shut down the engine in response to ademanded power level of the engine being below a threshold and based onone or more of an electrical demand from the one or more electricalcomponents and an amount of electrical energy stored at the generator.In another example, the method may comprise, after shutting down theengine, starting either the first turbocharger turbine or auxiliaryturbine coupled with the generator via energy stored at the generator.In yet another example, the method may further comprise, before shuttingdown the engine, starting either the first turbocharger turbine orauxiliary turbine coupled with the generator using exhaust energyproduced at the engine. In one example, adjusting the one or more valvesand operating the burner occurs while the engine is hot and includesdetermining an amount of opening of the valve and an amount of fuelinjected to the burner based on an electrical demand of the one or moreelectrical components. The method may further comprise, when the engineis operating, flowing exhaust gas to the first turbocharger turbine and,in response to a speed of the first turbocharger turbine being greaterthan desired for torque demand, recovering exhaust energy via thegenerator. In another example, the method may comprise, in response tothe speed of the first turbocharger turbine being less than desired fortorque demand, supplying energy from the generator to the firstturbocharger turbine to increase the speed of the first turbochargerturbine.

As yet another embodiment, a system comprises a first turbochargerincluding a first turbine disposed in an exhaust passage and a firstcompressor disposed in an intake passage, the first compressor driven bythe first turbine, where the exhaust passage is fluidly coupled to aplurality of non-donor cylinders; an exhaust gas recirculation (EGR)system fluidly coupled to a plurality of donor cylinders and including afirst EGR passage coupled between the intake passage and the pluralityof donor cylinders and a second EGR passage coupled between the firstEGR passage and the exhaust passage, where the first EGR passageincludes a first EGR valve and the second EGR passage includes a secondEGR valve; a fuel burner fluidly coupled to the exhaust passage upstreamof the first turbine and downstream of where the second EGR passagecouples to the exhaust passage; and a generator coupled to one of thefirst turbine or an auxiliary turbine coupled to the exhaust passagedownstream of the fuel burner. The system may further comprise a secondturbocharger including a second turbine disposed in the exhaust passagedownstream of the first turbine and a second compressor disposed in theintake passage upstream of the first compressor, the second compressordriven by the second turbine and where the generator is coupled to oneof the first turbine, the second turbine, or the auxiliary turbinecoupled to the exhaust passage downstream of the fuel burner. The systemmay further comprise an electrical component electrically coupled withthe generator and a controller including non-transitory memory withcomputer readable instructions for: shutting down the engine, adjustingthe first EGR valve and second EGR valve to provide air flow from theintake passage to the fuel burner, operating the fuel burner to produceexhaust gas, recovering energy from the exhaust gas via the generator,and powering the electrical component with the recovered energy.

As still another embodiment, a system comprises a first turbochargerincluding a first turbine disposed in an exhaust passage and a firstcompressor disposed in an intake passage, the first compressor driven bythe first turbine, where the exhaust passage is fluidly coupled to aplurality of cylinders; an engine bypass passage coupled between theintake passage and exhaust passage; a fuel burner disposed in one of:the engine bypass passage, the exhaust passage upstream of the firstturbine and downstream of where the engine bypass passage couples to theexhaust passage, or in a second bypass passage fluidly coupled to theexhaust passage upstream of the first turbine and downstream of wherethe engine bypass passage couples to the exhaust passage; and agenerator coupled to one of the first turbine or an auxiliary turbinecoupled to the exhaust passage downstream of the fuel burner. The systemmay further comprise a second turbocharger including a second turbinedisposed in the exhaust passage downstream of the first turbine and asecond compressor disposed in the intake passage upstream of the firstcompressor, the second compressor driven by the second turbine and wherethe generator is coupled to one of the first turbine, the secondturbine, or the auxiliary turbine coupled to the exhaust passagedownstream of the fuel burner. In another example, the system mayfurther comprise an electrical component electrically coupled with thegenerator and a controller including non-transitory memory with computerreadable instructions for: shutting down the engine, adjusting one ormore bypass valves disposed in one or more of the intake passage, enginebypass passage, or exhaust passage to provide air flow from the intakepassage to the fuel burner, operating the fuel burner to produce exhaustgas, recovering energy from the exhaust gas via the generator, andpowering the electrical component with the recovered energy.

As used herein, an element or step recited in the singular and proceededwith the word “a” or “an” should be understood as not excluding pluralof said elements or steps, unless such exclusion is explicitly stated.Furthermore, references to “one embodiment” of the invention do notexclude the existence of additional embodiments that also incorporatethe recited features. Moreover, unless explicitly stated to thecontrary, embodiments “comprising,” “including,” or “having” an elementor a plurality of elements having a particular property may includeadditional such elements not having that property. The terms “including”and “in which” are used as the plain-language equivalents of therespective terms “comprising” and “wherein.” Moreover, the terms“first,” “second,” and “third,” etc. are used merely as labels, and arenot intended to impose numerical requirements or a particular positionalorder on their objects.

The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

This written description uses examples to disclose the invention,including the best mode, and also to enable a person of ordinary skillin the relevant art to practice the invention, including making andusing any devices or systems and performing any incorporated methods.The patentable scope of the invention is defined by the claims, and mayinclude other examples that occur to those of ordinary skill in the art.Such other examples are intended to be within the scope of the claims ifthey have structural elements that do not differ from the literallanguage of the claims, or if they include equivalent structuralelements with insubstantial differences from the literal languages ofthe claims.

The invention claimed is:
 1. A system for an engine, comprising: a firstturbocharger including a first compressor driven by a first turbine, thefirst turbine disposed in an exhaust of the engine; a fuel burnerfluidly coupled to the exhaust upstream of the first turbine; agenerator coupled to one of the first turbine or an auxiliary, secondturbine fluidly coupled to the exhaust downstream of the fuel burner;one or more bypass valves configured to adjust a flow of air thatbypasses the engine and is delivered to the fuel burner; an enginebypass passage coupled between an intake of the engine and the exhaust,wherein the one or more bypass valves include a first bypass valvedisposed in an intake of the engine, downstream in the intake from wherethe engine bypass passage couples to the intake, and a second bypassvalve disposed in the exhaust, upstream in the exhaust from where thebypass passage couples to the exhaust, wherein the fuel burner isdisposed within the bypass passage, and wherein the fuel burner is theonly fuel burner coupled to the exhaust in the system; and a controllerwith computer readable instructions stored on non- transitory memorythat when executed when the engine is shut down, cause the controllerto: adjust the one or more bypass valves to flow air from the intake ofthe engine to the fuel burner, operate the fuel burner to produceexhaust gas, and recover exhaust energy from the produced exhaust gasvia the generator, in response to the engine being shut down and whilethe engine is shut down.
 2. The system of claim 1, further comprising anelectrical component electrically coupled with the generator and whereinthe instructions further include instructions that cause the controllerto operate the electrical component via energy stored in a battery ofthe generator while the engine is shut down.
 3. A system, comprising: afirst turbocharger including a first turbine disposed in an exhaustpassage and a first compressor disposed in an intake passage, the firstcompressor driven by the first turbine, where the exhaust passage isfluidly coupled to a plurality of cylinders; an engine bypass passagecoupled between the intake passage and the exhaust passage; one or morebypass valves disposed in one or more of the intake passage, the enginebypass passage, or the exhaust passage; a fuel burner disposed in oneof: the engine bypass passage, or in a second bypass passage fluidlycoupled to the exhaust passage upstream of the first turbine anddownstream of where the engine bypass passage couples to the exhaustpassage, wherein the fuel burner is the only fuel burner in the system;a generator coupled to one of the first turbine or an auxiliary turbinecoupled to the exhaust passage downstream of the fuel burner; and anelectrical component electrically coupled with the generators; and acontroller with computer readable instructions stored on non-transitorymemory that when executed when the engine is shut down, cause thecontroller to: adjust the one or more bypass valves to provide air flowfrom the intake passage to the fuel burner, and while the engine is shutdown: operate the fuel burner to produce exhaust gas, recover energyfrom the exhaust gas via the generator, and power the electricalcomponent with the recovered energy.